Digital radiography is an alternative to film-based imaging technologies that rely on photosensitive film layers to capture radiation exposure and thus to produce and store an image of a subject's internal physical features. With digital radiography, the radiation image exposures captured on radiation-sensitive layers are converted, pixel by pixel, to electronic image data which is then stored in memory circuitry for subsequent read-out and display on suitable electronic image display devices.
The primary objective of a radiographic imaging detector is to accurately reproduce the organ or the object that is being imaged, while exposing the patient (in medical and dental applications) or the object (in non-destructive testing) to a minimal amount of x-rays.
In digital radiography, scintillating screens are used to convert x-rays to visible radiation. The visible radiation is converted by photosensitive elements (e.g., amorphous silicon) into electrical signals that are processed by associated circuitry. In order to accurately image an organ or element, and at the same time, minimize the exposure of the patient or the object to the x-rays, it is necessary to place the scintillator screen in intimate contact with the photosensitive element, and ensure that the circuitry associated with the detection of the signal due to the radiation, is able to detect very small levels of electrical charge.
For example, creation of scintillator screens by coating a formulation of scintillator particles, polymeric binders, and other additives on a polymeric support is disclosed in U.S. Pat. Nos. 3,883,747 and 4,204,125. However, when these scintillator screens and the radiographic detectors are brought together in intimate contact, the sensitivity of the combination has to be manipulated to ensure that electrostatic discharge (ESD) events generated due to triboelectric phenomena do not induce artifacts in the radiographic image or damage the radiographic detector, which require fairly sophisticated & expensive processes to manufacture.
A number of approaches have been taken to minimize the impact of ESD events on digital radiographic detectors. The deposition of conductive coatings on the surface of the detector to spread out the charge generated by the ESD event and circuitry to dissipate the charge is described in U.S. Pat. Pub. 2010/0091149A1, U.S. Pat. Pub. 2008/0237481A1, U.S. Pat. Nos. 7,532,264 and 7,902,004. However, this approach leads to the decrease in the overall sensitivity of the photosensitive detector.
It would be desirable to minimize the probability of an ESD event due to tribocharging and to diminish the magnitude of the charge generated in the case of an ESD event, while maintaining the sensitivity of the photoelectric detector. In addition, it is necessary to mate the scintillator screen and the flat panel detector in a manner that does not degrade antistatic protection or hinder detection of the visible radiation by the flat panel detector.